"It's Been Standing So Long That....

it's pretty unlikely to fall down now!"

That's another odd piece of reasoning I hear frequently -- I just ran across it this morning in a work of fiction, in reference to a house, but I've also had it said to me personally, regarding other engineered works. Of course, everything has "been standing" until the very day it falls, so this almost predicts nothing will ever fall. And, of course, everything collapses eventually, so it would be more accurate to say, "This is getting closer to the day it will collapse every minute!"

I think the intuition is that, "If it's stood this long, it was built well." Now, it's true that if a bridge has held up for 80 years, that means it was engineered well enough to stand for 80 years! But the jury is entirely out, based on that fact, as to whether it was good enough engineering to keep it up for 80 years and 1 day. You could, of course, inspect the bridge and see if it's still sound, but that is exactly what this old saw is meant to discourage -- in fact, that was the exact situation in which I once heard it used:

6 comments:

I have awakened tens of thousands of days in a row alive. I think I may extrapolate with confidence unmatched for any scientific experiment in history (except perhaps one that gets done in all the schools) that I shall live forever.

Ha-ha-ha, Bob, that's funny! But of course my whole post is a piece of inductive reasoning -- in all these other cases we see things fall down after standing a long time, so in this case we will too.

Bob, everything true in Popper -- naive induction is bad, falsification is more important than verification -- was there in Bacon and Boyle, but Popper was too historically unaware to know this. Everything original in Popper -- confirmation means nothing -- is wrong!

Your post about the fact of a building standing for 80 years being as consistent with its being built so as to last ONLY 80 years, as it is with being built to last 'forever,' reminded me of a point that Wittgenstein makes in the Philosophical Investigations about pattern recognition, learning how to follow rules, and the moment of recognition that "I can go on now." What was that point, anyway?

It seems like, when multiple rules or principals can account for a finite number of observations generated by the 'true rule,' that induction alone will never provide sufficient grounds for determining which principle is actually generating the observations. And, in the end, something like a commitment to parsimony or elegance has to be brought in to make these kinds of determinations for you...